Glucose PTS modulates pyruvate metabolism, bacterial fitness, and microbial ecology in oral biofilm

Recently identified spontaneous mutants of major glucose-PTS (manLMNO) in stocks of Streptococcus sanguinis SK36 showed enhanced fitness in low-pH environment. Transcriptomic and metabolomic analyses of the manL mutant (SK36/manL) revealed redirection of pyruvate from production of lactate to acetate for extra energy extraction, resulting in excretion of greater amounts of pyruvate and H2O2, and increased expression of multiple alkali-generating activities. Genes showing increased expression in SK36/manL also included several carbohydrate transporters, putative extracellular glycosidases, intracellular polysaccharide (IPS) locus, pathways for catabolism of acetoin, ethanolamine, ascorbate, and formate, genes required for membrane biosynthesis, and those for motility and attachment. A wild-type S. sanguinis strain SK36 and its isogenic mutant deficient in glucose-PTS (manL) were each cultured (n = 3) to exponential phase in TY medium supplemented with 20 mM glucose, treated with RNAprotect reagent, and harvested for RNA extraction and RNA-Seq analysis